Yes, people are often selfish, and a great deal of our moral, political, and religious behavior can be understood as thinly veiled ways of pursuing self-interest. (Just look at the awful hypocrisy of so many politicians and religious leaders.) But it’s also true that people are groupish. We love to join teams, clubs, leagues, and fraternities. We take on group identities and work shoulder to shoulder with strangers toward common goals so enthusiastically that it seems as if our minds were designed for teamwork.
